its just pinking when its running out of fuel. all my bikes have done it... when its running out of fuel it gets leaner ( less fuel more air ) then runs hotter starts pinking. even full of fuel after a big rev or when hot mine pinks. pinking is when you open the throttle and it makes a mettalic clunking at the crack of throttle. hope you know what i mean . if its really bad give it a 1/4 turn out on the small screw on the carb ( there are two ) big one is idle. turning the small screw out ( anti clockwise ) will make it slightly richer. let me know how you get on.
shercoben12's post in Gas Gas Txt Pro 300 2013 Issue was marked as the answer